1. Field of the Invention
This invention relates to the field of internal combustion engines selected cylinders of which may be disabled to conserve fuel.
2. Prior Art
The internal combustion engine art has for many years been attempting to solve the problem of fuel being wasted during light load conditions due to the non-adjustment capabilities of the engine upon completion of heavy load requirements. Consequently, numerous approaches have been devised to provide an adjustment mechanism so that the engine will use less fuel during light load conditions. Typically, this is accomplished by disabling selected cylinders which ordinarily involves the interruption of the fuel flow. Some disclosures have gone as far as teaching the removal of several portions of the cylinder such that even during heavy load operation these cylinders are still ineffective, for example U.S. Pat. Nos. 3,874,358, 3,945,367 and 4,070,971. It is to be noted that in each of these references the intake and exhaust valves of the disabled cylinders are purposely maintained in a continuously closed orientation, providing an amount of vacuum and compression during the operation of the engine. To overcome this problem, U.S Pat. No. 3,874,358 teaches the substitution of pistons having passages therein to prevent these effects. U.S. Pat. No. 3,945,367 teaches connecting hoses to the opening from which the spark plug is removed to act as an intake and exhaust of air. U.S. Pat. No. 4,070,971 teaches the removal of the pistons altogether.
In an effort to maintain certain cylinders non-functional and yet maintain them in a condition for use during heavy load conditions, various push rod, rocker arm and valve devices have been described which may selectively or periodically disable particular cylinders. As was noted in U.S. Pat. No. 4,151,817 the prior U.S. patent art is replete with patents teaching valve disablement.
Few patents have included cam lobe modification in their attempt to solve the fuel waste problem. U.S. Pat. Nos. 2,934,052 and 3,277,874 disclose camshafts with high and low lift lobes for actuating each of the engine valves and means for causing the high or low lift lobe to so activate the valve. In U.S Pat. No. 2,934,052-Longenecker an actuating rod is utilized to shift the cam follower members from one lift lobe to another. However, it is specifically taught therein that none of the cylinders, on which these lift lobes operate are at any time disabled. U.S. Pat. No. 3,277,874-Wagner discloses long and short lift lobe surfaces in conjunction with a fluid operated cam follower which is apparently positioned at one end of a push rod. Apparently, fluid flowing through the cam follower will cause it to be in contact with one cam lobe surface or another.
U.S. Pat. No. 4,151,817 discloses an engine valve control mechanism wherein camshaft lobes comprise inner and outer surfaces and are caused to effect the valves of the engines disclosed therein through the use of a complex rocker arm and lash adjuster assembly. It is again shown in that reference that disablement of selected cylinders is maintained by closing both intake and exhaust valves. As was previously mentioned, vacuum and compression problems can occur if cylinders are disabled in this fashion.
U.S. Pat. No. 4,064,861-Schulz discloses an engine which allows selected cylinder disablement by interrupting the flow of the air-fuel mixture before it reaches the intake valve and by maintaining the exhaust valve in an open state. No provisions are made for the intake valve which will continue to open and close during the cylinder disablement.
None of the above cited references describes an internal combustion engine capable of selective cylinder disablement wherein the selected cylinders have cam activated exhaust and intake ports and cam lobes shaped to provide selective maintenance of the exhaust port in either a continuously or periodically opened condition and the intake port in either a continuously or periodically closed condition. In addition, none of the above-cited references disclose camshafts containing lobes with compound surfaces which are capable of longitudinal movement so that the various surfaces of the lobe can come to bear.